P Motor question

This may have been asked and answered earlier, but I could not find the thread...what was the purpose of those extravagant decks on both ends of the P motors (ex-CUT electrics) brought east in '55?

Thanks, Paul

I'll take a stab at it!
Pure speculation, they probably needed the large wheel base to spread the weight of the locomotive out over the rails but found all the electrical gear fit in a smaller car body thus not needing a full length one like the GG1, resulting in the large platforms.

Yes, weight distribution was apparently the reason. In 1907, an earlier S motor derailed while hauling a passenger train, killing many on board. The investigators determined that the relatively compact locomotive simply concentrated too much weight over too small an area, a condition that was further aggravated by excess speed and the inexperience of the engineer.

Subsequent boxcabs like the P motor were heavily beefed up in the wheel-and-axle department, resulting in significant weight gain, which for safety's sake needed to be spread over a greater track area.

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It should be remembered too that the Ps were never intended to the strictly terminal engines and switchers. They were built with eventual electrification of NYC's main line in mind, and thus were designed for maximum stability at high speeds. Their design, of course, was further refined on the NH's EP-4s and then the GG-1s.

I think the primary problem with the original S motors wasn't so much weight as the rigid frame (they were essentially 2-8-2s) combined with only a single leading/trailing axle. Rebuilding with a two-axle leading/trailing truck solved most of the problem, but all subsequent NYC electric classes had articulated frames.

In addition to the reasons already stated above for the adoption of the 4-wheel lead trucks, they have the advantage of guiding the mass of the engine into curves at high speed, just as the 4-wheel lead truck on a passenger steam locomotive is designed to do.

And, oh --- regarding the comment . .

Their design, of course, was further refined on the NH's EP-4s and then the GG-1s.

. . . That statement is correct, and I will, if I may, expand on it. The P's which I believe entered sevice in 1930 were indeed the first use of the 2-C+C-2 wheel arrangement. It was first copied on the New Haven's EP-3 class engines delivered in 1931, just a year after the P's. Those NH EP-3s generally resembled the Cleveland engines with their "front porches" and box cabs, although the EP-3's porches were not so long.

When designing the first GG-1 in about 1933, the PRR borrowed one of the NH engines for high speed tests and found the 2-C+C-2 arrangement was very superior to any other arrangement the PRR had tried on electric motors. Hence the 138 GG-1s were all built with running gear that was virtually a total copy of the NH EP-3s. NH ordered two later classes of electrics with the same running gear: the EP-4 passenger engines (1938) and the EF-3 freight motors (1942).

I had the great pleasure of a cab ride on one of the P's on the Harlem Division, about 1966. The articulation on the engine created an odd visual experience as I watched the movement of that long "front porch" as it stretched out ahead of the cab. Entering every curve, and every crossover, that porch swung right or left an observable interval before the body of the engine did!